It is known to inscribe keys by two-color injection moulding. In this method the inscription is injection moulded in a first step, and the key body which encases the inscription is injection moulded in a following process step. In order to facilitate satisfactory injection moulding, the inscription should not fall below specified minimum dimensions. Since special and expensive injection moulds are required for each inscription to produce keys in accordance with this method, this method can be economically employed only for large production runs.
It is also known to apply dark colored graphic symbols to light colored keys by means of thermal diffusion. In this method the appropriate color is first applied to the key body and is then caused to penetrate into the key body by intensive short-term heat treatment. This method is unsuitable for light colored inscriptions on a dark colored key body. The reason is that after the application of the light color and subsequent heating, the light color penetrates into the dark colored key body in such manner that the contours of the inscription become undetectable or unclear.
One object of the invention is to apply light colored inscriptions of arbitrary sizes to dark colored key bodies.